In recent years, with the rapid growth in the amount of data, the distributed database technology has also been rapidly developed. The distributed database technology divides data in an original centralized database into a large number of data slices, dispersedly stores them on a plurality of independent data storage nodes, and connects the physically dispersed plurality of data storage units to form a logically unified database. The distributed database technology uses a scalable system architecture where multiple servers are used to share the storage load, which not only improves the system reliability, availability and access efficiency, but also is easy to expand. In order to maintain the balanced distribution of data slices, when the number of data slices on a server among the overall distributed database system reaches a migration threshold, it is necessary to move data slices on a server which stores the maximum number of data slices to a server which stores less number of data slices. For example, if a data set has 100 data slices on a server A and 50 data slices on a server B, it is necessary to move data slices on the server A to the server B until the numbers of data slices of the data set on the two servers are close or equal.